Nine highly-productive NIH-funded investigators with nineteen NIH-funded projects (>$3,200,000 ADC) in two departments at Colorado State University request $341,154 in NCRR funds to purchase a Zeiss LSM 510 Confocal Laser Scanning Microscope to replace a now-defunct but previously heavily-used 10-year old Sarastro/Molecular Dynamics MultiProbe 2001 Confocal Microscope. In the past four years, the Department of Anatomy and Neurobiology has spent more than $47,000 to keep the Sarastro microscope functioning, but it has failed so often during critical experiments, and it is of such limited capability that it is now useful to only one group, which uses it solely to obtain low resolution maps of tissues for freeze-fracture analysis. Thus, members of all of the Major Users groups must either travel to other cities to obtain data, or they must rely on collaborators in other states and Canada to obtain publishable data. Scan rates for the Zeiss confocal are at least 20 times faster than the previous instrument (156 frames per minute vs. maximum of 8 frames per minute at 512x512), thereby permitting analysis of transient phenomena in living cells. The Zeiss LSM 510 as configured in this application has three lasers (ungradable to four), automated and reproducible image capture; three fluorescence channels (plus visible light) recorded simultaneously; and simultaneous interlaced dual laser scanning ("multi-tracking," not available on most other confocal systems). The latter capability allows image capture sufficiently rapidly to permit real-time analysis of biological processes in living cells (essential for at least 6 NIH-funded projects). Also important for a mult-iuser facility, the LSM 510 has a robust design and intuitive imaging software, with preset modes for both aboutroutine" and aboutexpert" users (which eliminates most manual adjustments). Confocal microscopy is essential in projects investigating calcium signaling, molecular composition of membranes, synaptic and non-synaptic mechanisms of neuronal transmission, and correlation of alterations in membrane molecularcomposition with changes in physiological activity and/or disease state. The Zeiss 510 will be installed in the Digital Imaging Center, whose operation is 100 percent funded by the Department of Anatomy and Neurobiology, allowing use of equipment at no ($0) hourly charge to users. A half-time Director will maintain the instrument and train new users. The DIC Board of Directors will meet bi-monthly to insure continued efficient scheduling and operation of the replacement confocal microscope, to consider future upgrades, and to establish or change DIC access policies.